Manufactured natural pozzolan, improved manufactured natural pozzolan-based cement and method of making and using same

ABSTRACT

The present invention comprises a product. The product comprises a first mineral in particulate form and having a first pozzolanic reactivity and a second mineral in particulate form and having a second pozzolanic reactivity greater than the first reactivity, wherein the surface of at least some of the particles of the first mineral is at least partially covered with particles of the second mineral. A method of making the composition of the present invention is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of application Ser. No. 62/404,021filed Oct. 4, 2016.

FIELD OF THE INVENTION

The present invention generally relates to an improved manufacturednatural pozzolan. More particularly, the present invention also relatesto a cementitious material containing an improved manufactured naturalpozzolan. The present invention further relates to concrete containingan improved manufactured natural pozzolan. The present invention alsorelates to a method of making an improved manufactured naturalpozzolan-based cementitious material. The present invention furtherrelates to a method of making concrete with a hydraulic cement and animproved manufactured natural pozzolan. The present invention furtherrelates to a method a making concrete with portland cement and animproved manufactured natural pozzolan. The present invention alsorelates to a method of making concrete comprising a cementitiousmaterial based on an improved manufactured natural pozzolan. Inaddition, the present invention relates to a method of curing concretecomprising an improved manufactured natural pozzolan or an improvedmanufactured natural pozzolan-based cementitious material.

BACKGROUND OF THE INVENTION

Concrete dates back at least to Roman times. The invention of concreteallowed the Romans to construct building designs, such as arches, vaultsand domes that would not have been possible without the use of concrete.Roman concrete, or opus caementicium, was made from a hydraulic mortarand aggregate or pumice. The hydraulic mortar was made from eitherquicklime, gypsum or pozzolana. Quick lime, also known as burnt lime, iscalcium oxide; gypsum is calcium sulfate dihydrate and pozzolana is afine, sandy volcanic ash (with properties that were first discovered inPozzuoli, Italy). The concrete made with volcanic ash as the pozzolanicagent was slow to set and gain strength. Most likely the concrete wasbuild up in multiple layers on forms that had to stay in place for avery long time. Although the concrete was slow to set and gain strength,over long periods of time it achieved great strength and was extremelydurable. There are still Roman concrete structures standing today as atestimony to the quality of the concrete produced over 2000 years ago.

Modern concrete is composed of one or more hydraulic cements, coarseaggregates, and fine aggregates. Optionally, modern concrete can includeother cementitious materials, inert fillers, property modifyingadmixtures and coloring agents. The hydraulic cement is typicallyportland cement. Other cementitious materials include Fly Ash, slagcement and other known natural pozzolanic materials. The term “pozzolan”is defined in ACI 116R as, “. . . a siliceous or siliceous and aluminousmaterial, which in itself possesses little or no cementitious value butwill, in finely divided form and in the presence of moisture, chemicallyreact with calcium hydroxide at ordinary temperatures to form compoundspossessing cementitious properties.”

Portland cement is the most common hydraulic cement used around theworld today. Portland cement is typically made from limestone. Concreteor mortar made with portland cement sets relatively quickly and gainsrelatively high compressive strength in a relatively short time.Although significant improvements have been made to the process andefficiency of portland cement manufacturing, it is still a relativelyexpensive and highly polluting industrial process.

Fly ash is a by-product of the combustion of pulverized coal in electricpower generation plants. When the pulverized coal is ignited in acombustion chamber, the carbon and volatile materials are burned off.When mixed with lime and water, Fly Ash forms a compound similar toportland cement. Two classifications of Fly Ash are produced accordingto the type of coal from which the Fly Ash is derived. Class F Fly Ashis normally produced from burning anthracite or bituminous coal thatmeets applicable requirements. This class of Fly Ash has pozzolanicproperties and will have minimum amounts of silica dioxide, aluminumoxide and iron oxide of 70%. Class F Fly Ash is generally used inhydraulic cement at dosage rates of 15% to 30% by weight, with thebalance being portland cement. Class C Fly Ash is normally produced fromlignite or subbituminous coal that meets applicable requirements. Thisclass of Fly Ash, in addition to pozzolanic properties, also has somecementitious properties. Class C Fly Ash is used in hydraulic cement atdosage rates of 15% to 40% by weight, with the balance being portlandcement.

Recently, the U.S. concrete industry has used an average of 15 milliontons of Fly Ash at an average portland cement replacement ratio ofapproximately 16% by weight. Since Fly Ash is a by-product from theelectric power generating industry, the variable properties of Fly Ashhave always been a major concern to the end users in the concreteindustry. Traditionally, wet scrubbers and flue gas desulfurization(“FGD”) systems have been used to control power plant SO₂ and SO₃emissions. The residue from such systems consists of a mixture ofcalcium sulfite, sulphate, and Fly Ash in water. In using sodium-basedreagents to reduce harmful emissions from the flue gas, sodium sulfiteand sulfate are formed. These solid reaction products are incorporatedin a particle stream and collected with the Fly Ash in particulatecontrol devices. There is the potential for the sodium-based reagent toreact with other components of the gas phases and with ash particulatesin the flue gas and in the particulate control device. All of theproducts of these reactions have the potential to impact the resultingFly Ash. Anecdotal evidence has shown that the Fly Ash that containssodium-based components has unpredictable and deleterious effect inconcrete. Consequently, the concrete industry is at great risk of usinga product that is unpredictable in its performance. Coupled with theclosure of many coal-fired power plants, resulting in less availabilityof Fly Ash, the concrete industry is facing a dramatic shortage of afamiliar pozzolan.

Known natural pozzolans can be used in concrete to replace the growingshortage of Fly Ash. However, known natural pozzolan deposits arelimited and generally are far from construction markets. Naturalpozzolans can be raw or processed. ASTM C-618 defined Class N naturalpozzolans as, “Raw or calcined natural pozzolans that comply with theapplicable requirements for the class as given herein, such as somediatomaceous earth; opaline chert and shales; tuffs and volcanic ashesor pumicites, any of which may or may not be processed by calcination;and various materials requiring calcination to induce satisfactoryproperties, such as some clays and shales.”

Other known natural pozzolans include Santorin earth, Pozzolana,Trachyte, Rhenish trass, Gaize, volcanic tuffs, pumicites, diatomaceousearth, and opaline shales, rice husk ash and Metakaolin. Santorin earthis produced from a natural deposit of volcanic ash of daciticcomposition on the island of Thera in the Agean Sea, also known asSantorin, which was formed about 1600-1500 B.C. after a tremendousexplosive volcanic eruption (Marinatos 1972). Pozzolana is produced froma deposit of pumice ash or tuff comprised of trachyte found near Naplesand Segni in Italy. Pozzolana is a product of an explosive volcaniceruption in 79 A.D. at Mount Vesuvius, which engulfed Herculaneum,Pompeii, and other towns along the bay of Naples. The deposit nearPozzuoli is the source of the term “pozzolan” given to all materialshaving similar properties. Similar tuffs of lower silica content havebeen used for centuries and are found in the vicinity of Rome. In theUnited States, volcanic tuffs and pumicites, diatomaceous earth, andopaline shales are found principally in Oklahoma, Nevada, Arizona, andCalifornia. Rice husk ash (“RHA”) is produced from rice husks, which arethe shells produced during the dehusking of rice. Rice husks areapproximately 50% cellulose, 30% lignin, and 20% silica. Metakaolin(Al₂O₃:2SiO₂) is a natural pozzolan produced by heatingkaolin-containing clays over a temperature range of about 600 to 900° C.(1100 to 1650° F.) above which it recrystallizes, rendering it mullite(Al₆Si₂O₁₃) or spinel (MgAl₂O₄) and amorphous silica (Murat, Ambroise,and Pera 1985). The reactivity of Metakaolin is dependent upon theamount of kaolinite contained in the original clay material. The use ofMetakaolin as a pozzolanic mineral admixture has been known for manyyears, but has grown rapidly since approximately 1985.

Natural pozzolans were investigated in this country by Bates, Phillipsand Wig as early as 1908 (Bates, Phillips, and Wig 1912) and later byPrice (1975), Meissner (1950), Mielenz, Witte, and Glantz (1950), Davis(1950), and others. They showed that concretes containing pozzolanicmaterials exhibited certain desirable properties such as lower cost,lower temperature rise, and improved workability. According to Price(1975), an example of the first large-scale use of portland-pozzolancement, composed of equal parts of Portland cement and a rhyoliticpumicite, is the Los Angeles aqueduct in 1910-1912. Natural pozzolans bytheir very definition have high silica or alumina and silica contenteither in a raw or calcined form.

Generally Fly Ash has the advantage that it can reduce water demand ofthe cementitious matrix. This reduces plastic shrinkage and allows forbetter workability. Generally, known natural pozzolans and silica fumeincrease water demand in the cementitious matrix; in some cases as highas 110%-115% that of portland cement. Greater water demand createsundesirable concrete properties such as lower strength development andgreater plastic shrinkage. It is desired that pozzolans have a waterdemand that is lower than or equal to portland cement. However this isan extremely rare occurrence for known natural pozzolans.

Due to the wide variety of natural pozzolanic types and quality, foundin generally relative small deposits and contamination with otherminerals makes it difficult to provide consistent pozzolan material onan industrial scale for a price comparable to the Fly Ash with similarand guaranteed performance required by the concrete industry. Inaddition since most of these deposits are found in the western part ofthe U.S., the transportation cost makes them prohibitive to use in therest of the country. Therefore it would be desirable to have sources ofnatural pozzolan distributed throughout the country. It would also bedesirable to have natural pozzolan having generally stable reactivitybased on consistent chemical properties.

Aggregate quarries that mine construction aggregate are ubiquitousthroughout the country. These aggregates chemical composition isprimarily based on silicon dioxide and have the chemical component toreact in a similar fashion as pozzolans. However these rock deposits aregenerally of crystalline type and are very slow to react even whenground to a sufficiently small particle size similar to other pozzolansor Fly Ash. While they may pass various sections of the ASTM C 618,overall they fail to meet other criteria. For example, these aggregatesof a particle size sufficient to pass particle size criteria of amaximum of 34% of the amount retained when wet-sieved on a 45-μm (No.325) sieve; they may pass the minimum requirement of 70% for total sumof silicon dioxide, iron oxide and aluminum oxide (SiO₂+Al₂O₃+Fe₂O₃),they may pass the requirement for the loss of ignition of a maximum of10% and pass the requirement of water demand of a maximum of 115% andthe autoclave expansion or contraction of a maximum of 0.8%. Yet, theytypically fail the strength activity index based on the reactivitycriteria of a minimum of 75% of control with portland cement, at 7 days,and the a minimum of 75% of control with portland cement, at 28 days. Inaddition, while some aggregates may pass all of the above ASTM D-618criteria they are well below the reactivity of portland cement or FlyAsh and therefore are undesirable for use in the market place.

The crystalline aspect of these aggregates may be changed to amorphousthrough calcination. However, calcination adds cost to the product andmakes such process relative expensive. It would be desirable to alterthe crystalline aspect of the fine particle size aggregate-basedmaterial by adding an amorphous component so that the reactivity indexincreases to pass ASTM C-618 at 7 and 28 days. It would also bedesirable to convert a low reactive material through a relativelyinexpensive process to enhance its reactivity index performance so thatit can meet or exceed the reactivity properties of Fly Ash or otherknown pozzolans.

SUMMARY OF THE INVENTION

The present invention satisfies the foregoing needs by providing anatural pozzolan that has improved properties and lower water demandthan known fine ground crystalline aggregate materials could be used asnatural pozzolans.

In one disclosed embodiment, the present invention comprises a product.The product comprises a first mineral in particulate form and having afirst pozzolanic reactivity and a second mineral in particulate form andhaving a second pozzolanic reactivity greater than the first reactivity,wherein the surface of at least some of the particles of the firstmineral is at least partially covered with particles of the secondmineral.

In another disclosed embodiment, the present invention comprises aprocess. The process comprises combining a first mineral in particulateform and having a first pozzolanic reactivity with a second mineral inparticulate form and having a second pozzolanic reactivity greater thanthe first reactivity, wherein the surface of at least some of theparticles of the first mineral is at least partially covered withparticles of the second mineral.

Accordingly, it is an object of the present invention to provide animproved concrete.

Another object of the present invention is to provide an improvedcementitious material.

A further object of the present invention is to provide an improvedsupplementary cementitious material.

Another object of the present invention is to provide an improvednatural pozzolan.

Another object of the present invention is to improve the reactivity ofa relatively low pozzolanic reactivity fine ground aggregate material.

These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiments and the appended claims.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

In one disclosure embodiment, the improved manufactured natural pozzolanof the present invention is made of a first mineral having a firstpozzolanic reactivity at least partially coated by a second mineralhaving a second pozzolanic reactivity higher than the first reactivity.The second mineral also has a smaller particle size than the firstmineral.

The first mineral is a crystalline or amorphous mineral aggregate with amaximum of approximately 25% by weight glass or amorphous content, ofapproximately 5% to approximately 60% by weight Plagioclase Feldspar, 0%to approximately 40% by weight Clinopyroxene, 0% to approximately 30% byweight Amphibole, 0% to approximately 30% by weight other minerals witha minimum of 45% by weight silicon dioxide (SiO₂) content including, butnot limited to, basalt, meta-basalt, intermediate, andesite or any othertype of rock, is ground to a fine particle size that passes a 45 μm (No.325) sieve, with a maximum of approximately 35% by volume retention. Theparticle size of the first mineral is approximately 15 to approximately60 μm (volume-based average particle size) or a particle size measuredby a specific surface area of approximately 50 to approximately 200m²/kg. The first mineral has a pozzolanic reactivity index of less than100% when tested in accordance with ASTM C-618 at 7 and 28 days. Thefirst mineral chemical composition is preferably approximately 45% toapproximately 60% SiO₂, approximately 5% to approximately 15% Al₂O₃,approximately 5% to approximately 20% Fe₂O₃, approximately 1% toapproximately 20% CaO, approximately 0.5% to approximately 12% MgO, 0%to approximately 5% N₂O, 0% to approximately 3% K₂O and approximately 1%to approximately 10% others compounds (all percentages are by weightunless otherwise noted).

The second mineral is an amorphous micro or nano silica, such as silicafume or any other type of nano or micro silica; or an aluminosilicate,such as Metakaolin, or any other type of calcined clay with a minimum of75% by weight aluminasilicate (Al₂O₃:2SiO₂), or any other type materialwith a minimum of 75% by weight glass or amourphous content, 0% toapproximately 20% Plagioclase Feldspar, 0% to approximately 10%K-Feldspar 0% to approximately 10% Clinopyroxene, 0% to approximately10% Amphibole, 0%to approximately 20% Kaolinite, 0% to approximately 10%Olivine, 0% to approximately 10% other minerals and a chemicalcomposition of approximately 50% to approximately 80% SiO₂,approximately 5% to approximately 45% Al₂O₃, approximately 5% toapproximately 20% Fe₂O₃, approximately 1% to approximately 20% CaO,approximately 0.5% to approximately 12% MgO, 0% to approximately 5% N₂O,0% to approximately 3% K₂O and approximately 1% to approximately 10%other compounds (all percentages are by weight unless otherwise noted)and a volume-based average particle size of approximately 0.1 toapproximately 10 μm or a specific area fineness of approximately 300 toapproximately 10,000 m²/kg. The second mineral has a pozzolanicreactivity index of greater than 100% when tested in accordance to ASTMC618 at 7 and 28 days. The properties above include all intermediatevalues.

The second mineral is then deposited, fused, coated or otherwisedisposed on to the surface of the first mineral. The proportion betweenthe two minerals is of approximately 70% to approximately 95% of thefirst mineral and approximately 5% to approximately 30% of the secondmineral when measured by weight or by volume. Various methods can beemployed to deposit, fuse, coat or otherwise disposed the second mineralonto the surface of the first mineral, such as blending through airmovement or electrostatic means. The particular method by which thecoating of the first mineral by the second mineral is accomplished isnot the subject of this inventions and can be any other means known inthe industry that can achieve the coating of this first mineral by thesecond mineral, fused or deposited onto the surface area of the firstmineral.

An alternative method of coating, depositing or otherwise disposing thesecond mineral onto the surface of the first mineral is byinter-grinding the second mineral with the first mineral. Yet anothermethod of coating, depositing or otherwise disposing the second mineralonto the surface of the first mineral is to employ autogenous grindingwhereby the two minerals of different particle size are aiding in thegrinding process itself. Another alternative method of coating,depositing or otherwise disposing the second mineral onto the surface ofthe first mineral is by mixing the first mineral with an aluminosilicateclay under elevated temperatures in a rotating kiln or blending andcalcining the two minerals together. Another alternative method offusing the second mineral onto the surface of the first mineral is byblending the two materials under elevated temperatures in a rotatingkiln or any other high temperature blending equipment.

The first mineral is slow to react on its own, however the secondmineral has a higher pozzolanic reactivity. As such the pozzolanicreaction starts on the surface of the first mineral that is highlyreactive due to the second mineral disposed thereon and then activatingthe first mineral that is less reactive. In other words the manufacturedpozzolan is activated by a two-stage pozzolanic reaction.

Preferably a water reducer admixture is added to the process above. Thewater reducing admixture will not affect the pozzolanic reaction,however it could improve the water demand based on various types ofaggregate and minerals used. Such water reducing admixtures are solidsor liquids. Water reducing admixtures are known in the industry andinclude, but are not limited to, lignin, naphthalene, carboxylates orpolycarboxylates.

Preferred types of aggregates for the first mineral are igneous rocks.Igneous rock deposits are generally consistent in their chemicalproperties. Also, there are many different mining tailing deposits, bothfrom closed and current mining operations, that meet the requirement ofa minimum 70% by weight for the total sum of silicon dioxide, iron oxideand aluminum oxide (SiO₂+Al₂O₃+Fe₂O₃) and can be used as the firstmineral.

The first mineral for use in the present invention can contain one ormore of olivine, pyroxene, magnetite, quartz, hornblende, biotite,hypersthene, feldspathoids, plagioclase, calcite or other crystallineminerals or mixtures thereof.

Basalt is an aphanitic (fine-grained) igneous rock with generally 45% to55% silica (SiO₂) containing essentially calcic plagioclase feldspar andpyroxene (usually Augite), with or without olivine. Basalts can alsocontain quartz, hornblende, biotite, hypersthene (an orthopyroxene) andfeldspathoids. Basalts are often porphyritic and can contain mantlexenoliths. Basalt is distinguished from pyroxene andesite by its morecalcic plagioclase. There are two main chemical subtypes of basalt:tholeiites which are silica saturated to oversaturated and alkalibasalts that are silica undersaturated. Tholeiitic basalt dominate theupper layers of oceanic crust and oceanic islands, alkali basalts arecommon on oceanic islands and in continental magmatism. Basalts canoccur as both shallow hypabyssal intrusions or as lava flows. Theaverage density basalt is approximately 3.0 gm/cm³.

Andesite is an abundant igneous (volcanic) rock of intermediatecomposition, with aphanitic to porphyritic texture. In a general sense,it is an intermediate type between basalt and dacite, and ranges from57% to 63% by weight silicon dioxide (SiO₂). The mineral assemblage istypically dominated by plagioclase plus pyroxene or hornblende.Magnetite, zircon, apatite, ilmenite, biotite, and garnet are commonaccessory minerals. Alkali feldspar can be present in minor amounts.

In a disclosed embodiment, the present invention comprises an improvedmanufactured natural pozzolan (i.e., the combination of the first andsecond minerals) in powder form. The particle size of the powder issufficiently small such that the improved manufactured natural pozzolanpowder has pozzolanic properties. The improved manufactured naturalpozzolan powder preferably having a volume average particle size (or avolume-based mean particle size) of less than or equal to 40 μm with amaximum 34% retained when passing through 325 mesh sieve, morepreferably less than or equal to 20 μm with a maximum of 34% retainedwhen passing through 325 mesh sieve, most preferably less than or equalto 15 μm with a maximum of 34% retained when passing through 325 meshsieve, especially less than or equal to 10 μm with a maximum of 34%retained when passing through 325 mesh sieve, more especially less thanor equal to 5 μm with a maximum of 34% retained when passing through 325mesh sieve. The foregoing ranges include all of the intermediate values.To achieve the desired particle size, the improved manufactured naturalpozzolan of the present invention can be ground using conventional meansincluding, but not limited to, a ball mill, a roll mill or plate mill. Aparticle size classifier can be used in conjunction with the mill toachieve the desired particle size. Equipment for grinding andclassifying the improved manufactured natural pozzolan to the desiredparticle size is commercially available from, for example, F. L. Smidth,Bethlehem, Pa.; Metso, Helsinki, Finland.

In one disclosed embodiment of the present invention, the improvedmanufactured natural pozzolan preferably has a chemical composition ofapproximately 45% to approximately 65% by weight SiO₂, approximately 5%to approximately 30% by weight Al₂O₃, approximately 5% to approximately15% by weight Fe₂O₃, approximately 5% to approximately 15% by weightCaO, approximately 1% to approximately 15% by weight MgO, less than orequal to approximately 5% by weight Na₂O. In addition to the foregoing,other compounds can be present in minor amounts, such as K₂O, TiO₂,P₂O₅, MnO, various metals, rare earth trace elements and otherunidentified elements. When combined, these other compounds representless than 10% by weight of the total chemical composition of theimproved manufactured natural pozzolan mineral.

In another disclosed embodiment, the improved manufactured naturalpozzolan in accordance with the present invention preferably has adensity or specific gravity of approximately 2.5 to approximately 3.1.

An improved manufactured natural pozzolan in accordance with the presentinvention is a combination of crystalline and amorphous (glassy)combination in varying proportions. Preferably, the improvedmanufactured natural pozzolan in accordance with the present inventionpreferably comprises approximately 0% to 99% by weight amorphous form,more preferably 10% to approximately 80% by weight amorphous form, mostpreferably approximately 20% to approximately 60% by weight amorphousform, especially approximately 30% to approximately 50% by weightamorphous form. The crystalline portion of the improved manufacturednatural pozzolan preferably comprises approximately 3% to approximately20% by weight olivine, approximately 5% to approximately 40% by weightclinopyroxene, approximately 5% to approximately 60% by weightplagioclase, and approximately 0% to approximately 10% (or less than10%) by weight other minerals including, but not limited to, magnetite,UlvoSpinel, quartz, feldspar, pyrite, illite, hematite, chlorite,calcite, hornblende, biotite, hypersthene (an orthopyroxene),feldspathoids sulfides, metals, rare earth minerals, other unidentifiedminerals and combinations thereof. The foregoing ranges include all ofthe intermediate values.

The improved manufactured natural pozzolan in accordance with thepresent invention can be used as a supplementary cementitious materialin concrete or mortar mixes. The improved manufactured natural pozzolanin accordance with the present invention is not by itself a hydrauliccement, but is activated by CaOH (hydrate lime) produced by thehydration of hydraulic cements, such as portland cement, or by otherminerals or compounds having reactive hydroxyl groups, such as CaO(quick lime). In addition the improved manufactured natural pozzolan inaccordance with the present invention when mixed with cement may improvethe cement nucleation process thereby improving the cement hydrationprocess. The improved manufactured natural pozzolan in finer particlesgenerally yields shorter set times and accelerated hydration in blendedcements. Finer particle size of the improved manufactured naturalpozzolan increases the rate of hydration heat development and early-agecompressive strength in portland cement. This acceleration may beattributable to the improved manufactured natural pozzolan particle size(nucleation sites), its crystalline make-up and chemical composition.The improved manufactured natural pozzolan in accordance with thepresent invention can be used in combination with any hydraulic cement,such as portland cement. Other hydraulic cements include, but are notlimited to, blast granulated slag cement, calcium aluminate cement,belite cement (dicalcium silicate), phosphate cements and others. Also,the improved manufactured natural pozzolan in accordance with thepresent invention by itself can be blended with lime to form acementitious material. In one disclosed embodiment, blended cementitiousmaterial for cement or mortar preferably comprises from approximately10% to approximately 90% by weight hydraulic cement and approximately10% to approximately 90% by weight of the improved manufactured naturalpozzolan in accordance with the present invention, more preferablyapproximately 20% to approximately 80% by weight hydraulic cement andapproximately 20% to approximately 80% by weight of the improvedmanufactured natural pozzolan in accordance with the present invention,most preferably approximately 30% to approximately 70% by weighthydraulic cement and approximately 30% to approximately 70% by weight ofthe improved manufactured natural pozzolan in accordance with thepresent invention, especially approximately 40% to approximately 60% byweight hydraulic cement and approximately 40% to approximately 60% byweight of the improved manufactured natural pozzolan in accordance withthe present invention, more especially approximately 50% by weighthydraulic cement and approximately 50% by weight of the improvedmanufactured natural pozzolan in accordance with the present invention.In another disclosed embodiment of the present invention, thecementitious material for concrete or mortar preferably comprisesapproximately 50% to approximately 90% by weight hydraulic cement andapproximately 10% to approximately 50% by weight of the improvedmanufactured natural pozzolan in accordance with the present invention.The foregoing ranges include all of the intermediate values.

The present invention can be used with conventional concrete mixes.Specifically, a concrete mix in accordance with the present inventioncomprises cementitious material, aggregate and water sufficient tohydrate the cementitious material. The cementitious material comprises ahydraulic cement and the improved manufactured natural pozzolan inaccordance with the present invention. The amount of cementitiousmaterial used relative to the total weight of the concrete variesdepending on the application and/or the strength of the concretedesired. Generally speaking, however, the cementitious materialcomprises approximately 25% to approximately 40% by weight of the totalweight of the concrete, exclusive of the water, or 300 lbs/yd³ (177kg/m³) of cement to 1,200 lbs/yd³ (710 kg/m³) of cement. In ultra highperformance concrete, the cementitious material exceeds the 40% byweight of the total weight of the concrete. The water-to-cement ratio byweight is usually approximately 0.25 to approximately 0.7. Relativelylow water-to-cement materials ratios by weight lead to higher strengthbut lower workability, while relatively high water-to-cement materialsratios by weight lead to lower strength, but better workability. Forhigh performance concrete and ultra high performance concrete, lowerwater-to-cement ratios are used, such as approximately 0.15 toapproximately 0.25. Aggregate usually comprises 70% to 80% by volume ofthe concrete. In ultra high performance concrete the aggregate is lessthan 70% of the concrete by volume. However, the relative amounts ofcementitious material to aggregate to water are not a critical featureof the present invention; conventional amounts can be used.Nevertheless, sufficient cementitious material should be used to produceconcrete with an ultimate compressive strength of at least 1,000 psi,preferably at least 2,000 psi, more preferably at least 3,000 psi, mostpreferably at least 4,000 psi, especially up to about 10,000 psi ormore. In particular, ultra high performance concrete, concrete panels orconcrete elements with compressive strengths of over 20,000 psi can becast and cured using the present invention.

The aggregate used in the concrete in accordance with the presentinvention is not critical and can be any aggregate typically used inconcrete. The aggregate that is used in the concrete depends on theapplication and/or the strength of the concrete desired. Such aggregateincludes, but is not limited to, fine aggregate, medium aggregate,coarse aggregate, sand, gravel, crushed stone, lightweight aggregate,recycled aggregate, such as from construction, demolition and excavationwaste, and mixtures and combinations thereof.

The reinforcement of the concrete in accordance with the presentinvention is not a critical aspect of the present invention, and, thus,any type of reinforcement required by design requirements can be used.Such types of concrete reinforcement include, but are not limited to,deformed steel bars, cables, post tensioned cables, pre-stressed cables,fibers, steel fibers, mineral fibers, synthetic fibers, carbon fibers,steel wire fibers, mesh, lath, and the like.

The preferred cementitious material for use with the present inventioncomprises portland cement. The cementitious material preferablycomprises a reduced amount of portland cement and an increased amount ofsupplementary cementitious materials; i.e., the improved manufacturednatural pozzolan in accordance with the present invention. This resultsin cementitious material and concrete that is more environmentallyfriendly. The portland cement can also be replaced, in whole or in part,by one or more pozzolanic materials. Portland cement is a hydrauliccement. Hydraulic cements harden because of a hydration process; i.e., achemical reaction between the anhydrous cement powder and water. Thus,hydraulic cements can harden underwater or when constantly exposed towet weather. The chemical reaction results in hydrates that aresubstantially water-insoluble and so are quite durable in water.Hydraulic cement is a material that can set and harden submerged inwater by forming insoluble products in a hydration reaction. Otherhydraulic cements useful in the present invention include, but are notlimited to, calcium aluminate cement, belite cement (dicalciumsilicate), phosphate cements and anhydrous gypsum. However, thepreferred hydraulic cement is portland cement.

In a disclosed embodiment of the present invention, concrete or mortarcomprises a hydraulic cement, the improved manufactured natural pozzolanin accordance with the present invention, aggregate and water.Preferably, the cementitious material used to form the concrete ormortar comprises portland cement and the improved manufactured naturalpozzolan powder, more preferably portland cement and the improvedmanufactured natural pozzolan having a volume average particle size (orvolume-based mean particle size) of less than or equal to approximately40 μm with a maximum of 34% retained when passing through 325 meshsieve, most preferably portland cement and the improved manufacturednatural pozzolan having a volume average particle size of less than orequal to approximately 20 μm with a maximum of 34% retained when passingthrough 325 mesh sieve, preferably less than or equal to 15 μm with amaximum of 34% retained when passing through 325 mesh sieve, preferablyless than or equal to 10 μm with a maximum of 34% retained when passingthrough 325 mesh sieve, more preferably less than or equal to 5 μm witha maximum of 34% retained when passing through 325 mesh sieve. Theforegoing ranges include all of the intermediate values.

In another disclosed embodiment of the present invention, concreteincluding an improved manufactured natural pozzolan in accordance withthe present invention can include any other pozzolan in combination withhydraulic cement.

The portland cement and the improved manufactured natural pozzolan inaccordance with the present invention can be combined physically ormechanically in any suitable manner and is not a critical feature of thepresent invention. For example, the portland cement and the improvedmanufactured natural pozzolan in accordance with the present inventioncan be mixed together to form a uniform blend of dry cementitiousmaterial prior to combining with the aggregate and water. Or, theportland cement and the improved manufactured natural pozzolan inaccordance with the present invention can be added separately to aconventional concrete mixer, such as a transit mixer of a ready-mixconcrete truck, at a batch plant. The water and aggregate can be addedto the mixer before the cementitious material, however, it is preferableto add the cementitious material first, the water second, the aggregatethird and any makeup water last.

Chemical admixtures can also be used with the concrete in accordancewith the present invention. Such chemical admixtures include, but arenot limited to, accelerators, retarders, air entrainments, plasticizers,superplasticizers, coloring pigments, corrosion inhibitors, bondingagents and pumping aid.

Mineral admixtures can also be used with the concrete in accordance withthe present invention. Although mineral admixtures can be used with theconcrete of the present invention, it is believed that mineraladmixtures are not necessary. However, in some embodiments it may bedesirable to include a water reducing admixture, such as asuperplasticizer.

Concrete can also be made from a combination of portland cement andpozzolanic material or from pozzolanic material alone. There are anumber of pozzolans that historically have been used in concrete. Apozzolan is a siliceous or siliceous and aluminous material which, initself, possesses little or no cementitious value but which will, infinely divided form and in the presence of water, react chemically withcalcium hydroxide at ordinary temperatures to form compounds possessingcementitious properties (ASTM C618). The broad definition of a pozzolanimparts no bearing on the origin of the material, only on its capabilityof reacting with calcium hydroxide and water. The general definition ofa pozzolan embraces a large number of materials, which vary widely interms of origin, composition and properties The most commonly usedpozzolans today are industrial by-products, such as slag cement (groundgranulated blast furnace slag), Fly Ash, silica fume from siliconsmelting, and natural pozzolans such as highly reactive Metakaolin, andburned organic matter residues rich in silica, such as rice husk ash.

The improved manufactured natural pozzolan in accordance with thepresent invention is a previously unknown natural pozzolan. It can beused as a substitute for any other pozzolan or in combination with anyone or more pozzolans that are used in combination with any hydrauliccement used to make concrete or mortar.

It is specifically contemplated as a part of the present invention thatconcrete formulations including an improved manufactured naturalpozzolan in accordance with the present invention can be used withconcrete forms or systems that retain the heat of hydration toaccelerate the curing of the concrete. Therefore, in another disclosedembodiment of the present invention, concrete in accordance with thepresent invention can be cured using concrete forms such as disclosed inU.S. Pat. Nos. 8,555,583; 8,756,890; 8,555,584; 8,532,815; 8,877,329;9,458,637; 8,844,227 and 9,074,379 (the disclosures of which are allincorporated herein by reference); published patent applicationPublication Nos. 2014/0333010; 2014/0333004 and 2015/0069647 (thedisclosures of which are all incorporated herein by reference) and U.S.patent application Ser. No. 15/418,937 filed Jan. 30, 2017 (thedisclosure of which is incorporated herein by reference).

The following examples are illustrative of selected embodiments of thepresent invention and are not intended to limit the scope of theinvention. All percentages are by weight unless noted otherwise.

EXAMPLE 1

The first mineral is a basalt-type aggregate with a chemical make-up ofapproximately 48% SiO₂, 13% Al₂O₃, 10% Fe₂O₃, 12% CaO, 10% MgO, 1.5%N₂O, 0.3% K₂O and the balance being other compounds. The basalt-typeaggregate has an amorphous content of approximately 15% of approximately30% clinopyroxene, approximately 40% plagioclase feldspar, approximately15% olivine and the balance being other minerals. The basalt-typeaggregate is placed in a ball mill and ground to a volume-based averageparticle size of 30 microns. The second mineral is metakolin with achemical make-up of approximately 53% SiO₂, 40% Al₂O₃, 3% Fe₂O₃, 0.5%CaO, 0.5% MgO, 0.1% N₂O, 1% K₂O, and approximately 75% by weightamorphous content, of approximately 3% by weight K-feldspar,approximately 10% kaolinite and the balance being other minerals, withan average volume-based particle size of approximately 10 microns. Thebasalt-type aggregate particles and the Metakaolin particles are blendedtogether with a proportion of 80% basalt-type aggregate particles and20% Metakaolin. The resulting product has Metakaolin particles disposedon the surface of the basalt-type aggregate particles. The resultingimproved manufactured pozzolan has improved properties in accordancewith the present invention.

EXAMPLE 2

The first mineral is a basalt-type aggregate with a chemical make-up ofapproximately 48% SiO₂, 13% Al₂O₃, 10% Fe₂O₃, 12% CaO, 10% MgO, 1.5%N₂O, 0.3% K₂O and the balance being other compounds. The basalt-typeaggregate has no amorphous content of approximately 35% clinopyroxene,approximately 50% plagioclase feldspar, approximately 15% olivine andthe balance being other minerals.

The basalt-type aggregate is placed in a ball mill and ground to avolume-based average particle size of 20 microns. The second mineral issilica fume with a chemical make-up of approximately 98% SiO₂ and thebalance being other elements and having a volume-based average particlesize of 1 micron. The basalt-type aggregate particles and the silicafume particles are blended together with a proportion of 85% basalt-typeaggregate particles and 15% silica fume particles. The resulting producthas silica fume particles disposed on the surface of the basalt-typeaggregate particles. The resulting improved manufactured pozzolan hasimproved properties in accordance with the present invention.

EXAMPLE 3

The first mineral is a basalt-type aggregate with a chemical make-up ofapproximately 55% SiO₂, 15% Al₂O₃, 8% Fe₂O₃, 9% CaO, 4% MgO, 3% N₂O,0.9% K₂O and the balance being other compounds. The basalt-typeaggregate has no amorphous content of approximately 18% clinopyroxene,approximately 5% K-feldspar, approximately 10% Clino-amphibole and thebalance being other minerals. The basalt-type aggregate is placed in aball mill and ground to a volume-based average particle size of 30microns. The second mineral is metakolin with a chemical make-up ofapproximately 53% SiO₂, 40% Al₂O₃, 3% Fe₂O₃, 0.5% CaO, 0.5% MgO, 0.1%N₂O, 1% K₂O, and approximately 75% by weight amorphous content, ofapproximately 3% by weight K-feldspar, approximately 10% kaolinite andthe balance being other minerals, with an average volume-based particlesize of approximately 10 microns. The basalt-type aggregate particlesand the Metakaolin particles are blended together with a proportion of70% basalt-type aggregate particles and 30% Metakaolin. The resultingproduct has Metakaolin particles disposed on the surface of thebasalt-type aggregate particles. The resulting improved manufacturedpozzolan has improved properties in accordance with the presentinvention.

It should be understood, of course, that the foregoing relates only tocertain disclosed embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A process comprising combining a first mineral inparticulate form having a volume-based average particle size ofapproximately 15 to approximately 60 μm and having a first pozzolanicreactivity with a second mineral in particulate form having avolume-based average particle size of approximately 0.1 to approximately10 μm and having a second pozzolanic reactivity greater than the firstmineral pozzolanic reactivity, wherein the surface of at least some ofthe particles of the first mineral is at least partially covered withparticles of the second mineral; wherein the first mineral comprises:approximately 45% to approximately 55% by weight SiO₂ approximately 5%to approximately 15% Al₂O₃, approximately 5% to approximately 20% Fe₂O₃and approximately 1% to approximately 20% CaO; and an amorphous contentof less than or equal to 25% by weight and approximately 5% toapproximately 60% by weight Plagioclase Feldspar; and wherein the secondmineral comprises metakaolin.
 2. The process of claim 1 furthercomprising combining the first and second minerals with a hydrauliccement.
 3. The process of claim 2, wherein the hydraulic cement isportland cement.
 4. The process of claim 1, wherein the first mineralhas a pozzolanic reactivity of less than 100% as measured by ASTM C-618.5. The process of claim 1, wherein the second mineral has a pozzolanicreactivity of greater than 100% as measured by ASTM C-618.
 6. A processcomprising combining a first mineral in particulate form having avolume-based average particle size of approximately 15 to approximately60 μm and having a first pozzolanic reactivity with a second mineral inparticulate form having a volume-based average particle size ofapproximately 0.1 to approximately 10 μm and having a second pozzolanicreactivity greater than the first mineral pozzolanic reactivity, whereinthe surface of at least some of the particles of the first mineral is atleast partially covered with particles of the second mineral; whereinthe first mineral comprises: approximately 45% to approximately 55% byweight SiO₂ approximately 5% to approximately 15% Al₂O₃, approximately5% to approximately 20% Fe₂O₃ and approximately 1% to approximately 20%CaO; and an amorphous content of less than or equal to 25% by weight andapproximately 5% to approximately 60% by weight Plagioclase Feldspar;and wherein the second mineral comprises silica fume.
 7. The process ofclaim 6 further comprising combining the first and second minerals witha hydraulic cement.
 8. The process of claim 7, wherein the hydrauliccement is portland cement.
 9. The process of claim 6, wherein the firstmineral has a pozzolanic reactivity of less than 100% as measured byASTM C-618.
 10. The process of claim 6, wherein the second mineral has apozzolanic reactivity of greater than 100% as measured by ASTM C-618.11. A process comprising combining a first mineral in particulate formhaving a volume-based average particle size of approximately 15 toapproximately 60 μm and having a first pozzolanic reactivity with asecond mineral in particulate form having a volume-based averageparticle size of approximately 0.1 to approximately 10 μm and having asecond pozzolanic reactivity greater than the first mineral pozzolanicreactivity, wherein the surface of at least some of the particles of thefirst mineral is at least partially covered with particles of the secondmineral; wherein the first mineral comprises: approximately 45% toapproximately 55% by weight SiO₂ approximately 5% to approximately 15%Al₂O₃, approximately 5% to approximately 20% Fe₂O₃ and approximately 1%to approximately 20% CaO; and an amorphous content of less than or equalto 25% by weight and approximately 5% to approximately 60% by weightPlagioclase Feldspar; and wherein the second mineral comprises analuminosilicate.
 12. The process of claim 11 further comprisingcombining the first and second minerals with a hydraulic cement.
 13. Theprocess of claim 12, wherein the hydraulic cement is portland cement.14. The process of claim 11, wherein the first mineral has a pozzolanicreactivity of less than 100% as measured by ASTM C-618.
 15. The processof claim 11, wherein the second mineral has a pozzolanic reactivity ofgreater than 100% as measured by ASTM C-618.